Over the production lifetime of a wellbore, the subterranean formation through which the wellbore extends may be stimulated to enhance hydrocarbon recovery from the formation. Methods such as hydraulic fracturing (i.e., “fracking”) may enhance hydrocarbon recovery from the subterranean formation. In hydraulic fracturing operations, a hydraulic fracture is formed by injecting a high pressure fluid (e.g., water) including a proppant material (e.g., sand, ceramics, etc.) into a targeted portion of the subterranean formation at conditions sufficient to cause the formation material to fracture. Under the pressures of the hydraulic fracturing process, the proppant is forced into the fractures where the proppant remains, forming open channels through which reservoir fluid (e.g., oil or gas) may pass once the hydraulic fracturing pressure is reduced.
Frequently, radioactive tracers or other tracer materials are injected into the formation at the time of hydraulic fracturing to monitor the effectiveness of the fracturing process, identify patterns of fluid movement within the formation, fracture development, and connectivity within the reservoir. The information obtained may be used by operators to plan and/or modify stimulation treatment and completion plans to further enhance hydrocarbon recovery.
Another method of monitoring the formation, the reservoir, and fluid movement within the subterranean formation includes a technique referred to as “microseismic frac mapping.” Microseismic frac mapping includes locating microseismic events associated with fractures to determine the geometry of the fractures and estimate the effective production volume. An array of geophones positioned in an observation well near the completion well or an array of near-surface sensors are used to measure microseismic activity.
However, the use of such radioactive tracers and monitoring techniques is costly, difficult to apply in real time, frequently requires an observation well for the necessary equipment, and may contaminate nearby aquifers.